The invention relates to the lighting arts. It is especially applicable to the retro-fitting of incandescent light source-based traffic signals with higher efficiency and a more durable light emitting diode (LED)-based light source, and will be described with particular reference thereto. However, the invention will also find application in numerous types of lamps, flashlights, and other illuminators which presently employ inefficient incandescent or fluorescent light bulbs that have high failure rates principally due to filament fragility or fluorescent tube failure. The invention provides LED-based light sources which are safer and have improved versatility and greater compatibility with existing lighting standards.
With reference to FIG. 1, a conventional traffic signal ball 10 such as is used in the ubiquitous three-color (red, yellow, green) traffic control signal is schematically shown. The traffic signal ball 10 is suitable for providing the red, yellow, or green light of a three-color traffic signal, and includes an incandescent light bulb 12 which emits light via a filament 14 which glows when driven by an electrical current. The light bulb 12 includes a threaded electrical connector 16 adapted for connection to a threaded socket 18. The threaded socket 18 and the threaded electrical connector 16 cooperate to transmit electrical power from electrical conductors 20 to the filament 14. Light produced by the light bulb 12 is collected by traffic signal optics including a reflector 22, which is typically a parabolic reflector, and a lens 24 to produce a light beam outwardly directed from the traffic signal ball 10 with a suitable beam spread. The beam spread should be narrow enough to direct the light toward roadway users with a high degree of efficiency, but wide enough so that roadway users including pedestrians at the periphery of the road and drivers a substantial distance from the intersection can readily see the signal.
The aforementioned components are arranged within a traffic signal ball housing 26 having a cover 28 which typically includes the lens 24. The cover 28 is selectively opened, typically in a hinged manner, to provide access to the light bulb 12 for bulb replacement. The cover 28 optionally includes additional elements such as a visor or a tinted filter (elements not shown) for spectrally filtering the light to produce a red, green, or yellow output. The tinted filter is optionally incorporated into the lens 24 by tinting the lens material. The light bulb 12 typically produces a white light which is colored by passing through the tinted filter or tinted lens 24 to produce one of the red, yellow, and green lights of a known three-ball traffic light. For traffic signal balls providing a shaped light such as a left turn arrow, an xe2x80x9cXxe2x80x9d lane marker indicating xe2x80x9cwrong wayxe2x80x9d, a pedestrian xe2x80x9cwalkxe2x80x9d or xe2x80x9cdon""t walkxe2x80x9d signal, or the like, a masking filter (not shown) is typically included with the cover 28 to define the selected shape.
The conventional incandescent traffic signal ball 10 suffers from some disadvantages. The light bulb 12 frequently fails, usually due to a failure of the filament 14. Light bulb replacement is inconvenient, and the intersection is uncontrolled or improperly controlled and unsafe until the failed light bulb 12 is replaced. Furthermore, those skilled in the art will appreciate that the optical components such as the reflector 22 and the lens 24 which direct the white light produced by the light bulb 12 toward roadway traffic can also operate to reflect sunlight or other external light sources outward toward traffic, with the reflected light tinted according to the tinted filter or lens 24. Re-directed external light, known as xe2x80x9cphantomxe2x80x9d light, can confuse roadway users into believing the traffic signal ball 10 is lit when it is not. In some incandescent traffic signal balls, an anti-phantom optical component is included to reduce phantom light. In spite of these disadvantages, however, incandescent traffic light signals are the predominant technology in use today.
The frequency of light source replacement in a traffic light can be reduced by replacing the light bulb 12 with a light source employing light emitting diodes (LEDs), which are more durable and longer-lasting than incandescent sources. However, retro-fitting the traffic signal ball 10 with an LED-based light source is complicated by the very different electrical and optical characteristics of the LED versus the incandescent source. The light bulb filament 14 acts as an approximate point or line light source, and the optics of the traffic signal ball 10 are designed around such a source. An LED, in contrast, produces generally forwardly directed light. Furthermore, a single LED typically exhibits low optical power output, and so LED-based light sources usually employ a plurality of LEDs, further complicating attempts to shape the light distribution using conventional traffic signal ball optics.
A number of LED-based light sources have been developed for retro-fitting a conventional incandescent traffic signal ball 10. Examples can be found in U.S. Pat. Nos. Des. 388,726 and 6,268,801 both issued to Wu, U.S. Pat. No. 6,283,613 issued to Schaffer, U.S. Pat. No. 6,054,932 issued to Gartner et al., U.S. Pat. No. 5,898,381 issued to Gartner et al., and U.S. Pat. No. 5,782,555 issued to Hochstein. These LED-based light sources employ arrays of LEDs distributed to substantially conform to the desired light shape (a round circle or a left-turn arrow, for example) mounted onto a cover that replaces the cover 28 of the traffic signal ball 10. These sources retro-fit the cover 28, and therefore are configured to match the size, shape, and attachment mechanism of the cover 28. As a result, these sources are highly specific to the signal ball being retro-fitted, and have limited interchangeability. Since the replacement of an incandescent source by an LED source is typically performed in the field under tight time constraints, the maintenance crew must ascertain beforehand exactly which LED light source is needed, and obtain that source.
Another disadvantage of past methods for LED-based retro-fitting of the incandescent signal ball 10 is that it fails to make use of the existing components of the incandescent signal ball 10. Schaffer (U.S. Pat. No. 6,283,613), for example, points out that typical LEDs without associated optics produce a light beam with spatial characteristics that do not comply with Institute of Transportation Engineers (ITE) requirements and other regulations, and teaches incorporating individual optics associated with each LED in the retro-fit array. This introduces additional cost to the LED-based source and does not make use of the existing signal ball optics. Similarly, some past retro-fit methods have required extensive re-wiring of the electrical connections within the traffic light, negating the convenience, simplicity, and speed of conventional light bulb replacement.
Yet another disadvantage associated with some past LED retro-fitting methods is that, because at least the cover 28 is replaced, the signal ball 10 is no longer suitable for operation with an incandescent source. In some retro-fits, the reflector and other optical components are additionally removed. In view of the present predominance of incandescent light sources in traffic signaling, the practical and commercial viability of LED retro-fitting is hindered by retro-fitting which renders the traffic light unsuitable for use with incandescent light bulbs.
The present invention contemplates an improved LED-based light source apparatus and method for retro-fitting an incandescent signal light therewith that overcomes the above-mentioned limitations and others.
In accordance with one embodiment of the present invention, a traffic signal ball is disclosed, including a lamp having a plurality of LEDs, an optical element arranged to disperse forwardly directed light produced by the LEDs, and a threaded electrical connector. The lamp also includes an optical system that receives light dispersed by the optical element and forms at least a portion of the received light into an outwardly directed beam.
In accordance with another embodiment of the present invention, a method is provided for retro-fitting a traffic signal lamp with a threaded LED light source. The traffic signal lamp has a threaded light bulb, a threaded socket for receiving and powering the light bulb, and optics configured to direct light produced by the light bulb in a generally forward direction. The method includes the steps of removing the threaded light bulb from the threaded socket, and connecting the threaded LED light source into the threaded socket. The threaded LED light source includes: a threaded electrical connector adapted for mechanical and electrical connection to the threaded socket; at least one light emitting diode (LED); a heat-sinking element for removing heat from the at least one LED; electrical conditioning circuitry that receives electrical power from the threaded electrical connector and conditions the electrical power to operate the at least one LED; and an optical element optically communicating with the at least one LED for distributing light produced by the at least one LED in conformance with the traffic signal lamp optics.
In accordance with another embodiment of the present invention, a light-emitting diode-based light source is disclosed, for retro-fitting into a traffic signal lamp employing an incandescent light bulb. The light-emitting diode-based light source includes at least one light emitting diode (LED), a reflector cooperating with the at least one LED to adapt light produced by the at least one LED for receipt by optics of the traffic signal lamp, and a screw-type electrical connector adapted to mate with a threaded socket connector of the traffic signal lamp. The screw-type electrical connector is adapted to transmit electrical power to the at least one LED.
In accordance with yet another embodiment of the present invention, an LED-based light source is disclosed. A threaded electrical connector is arranged to receive electrical power. Power converting electronics receive the electrical power and convert the electrical power to converted power. A plurality of LEDs receives the converted power. The LEDs produce a generally forwardly directed first light beam responsive to receipt of the converted power. A light dispersing element is arranged at a focal region of a reflector and intercepts and transforms the first light beam into dispersed light emanating from the focal region. An optical system is arranged to focus the dispersed light emanating from the focal region into an output light beam having selected beam characteristics. The threaded electrical connector, the plurality of LEDs. the light dispersing element, the collimating reflector. and the lens comprise a unitary threadedly connectable light source.
In accordance with still yet another embodiment of the present invention, a lamp is disclosed for use in a light producing apparatus having a socket through which power is supplied to the lamp, which socket also holds the lamp, and an optical system including a reflector and a lens which cooperate to direct light outwardly from the light producing apparatus. The lamp includes a connector by which the lamp is installed in the socket, a number of LEDs electronically connected to the connector, and a redirection element arranged to redirect light emitted from the number of LEDs such that the redirected light is coupled into the optical system of the light producing apparatus.
One advantage of the present invention is that it replaces the light bulb of a traffic light ball or other incandescent lighting system with an LED-based light source in a manner which utilizes the existing optical and electrical components which are adapted for use with the light bulb, such as the reflector, lens, and electrical socket. This enables the lighting system to be optionally re-fitted with an incandescent light bulb at a later date in the usual manner.
Another advantage of the present invention resides in the operative cooperation of the present LED-based light source with the existing optics and filters of the traffic light ball. Filters providing selected color or graphical features (such as turn arrows or lane xe2x80x9cXxe2x80x9d indicators) are operatively retained, and so the LED-based light source is usable in many types of traffic light balls and in any of the red, yellow, or green signals. This simplifies field maintenance and reduces the number and type of LED-based light sources in traffic department inventories.
Yet another advantage of the present invention is that the LED-based light source includes a conventional threaded electrical connector and can be installed in the traffic light ball with the traffic light ball fully energized. The conventional threaded connector increases worker safety during installation, and the ability to perform the installation without first de-energizing the traffic light simplifies the installation process and reduces traffic delays.
Numerous other advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description.